1 // SPDX-License-Identifier: GPL-2.0 2 3 use super::HasHrTimer; 4 use super::HrTimer; 5 use super::HrTimerCallback; 6 use super::HrTimerCallbackContext; 7 use super::HrTimerHandle; 8 use super::HrTimerMode; 9 use super::HrTimerPointer; 10 use super::RawHrTimerCallback; 11 use crate::prelude::*; 12 use core::ptr::NonNull; 13 14 /// A handle for a [`Box<HasHrTimer<T>>`] returned by a call to 15 /// [`HrTimerPointer::start`]. 16 /// 17 /// # Invariants 18 /// 19 /// - `self.inner` comes from a `Box::into_raw` call. 20 pub struct BoxHrTimerHandle<T, A> 21 where 22 T: HasHrTimer<T>, 23 A: crate::alloc::Allocator, 24 { 25 pub(crate) inner: NonNull<T>, 26 _p: core::marker::PhantomData<A>, 27 } 28 29 // SAFETY: We implement drop below, and we cancel the timer in the drop 30 // implementation. 31 unsafe impl<T, A> HrTimerHandle for BoxHrTimerHandle<T, A> 32 where 33 T: HasHrTimer<T>, 34 A: crate::alloc::Allocator, 35 { 36 fn cancel(&mut self) -> bool { 37 // SAFETY: As we obtained `self.inner` from a valid reference when we 38 // created `self`, it must point to a valid `T`. 39 let timer_ptr = unsafe { <T as HasHrTimer<T>>::raw_get_timer(self.inner.as_ptr()) }; 40 41 // SAFETY: As `timer_ptr` points into `T` and `T` is valid, `timer_ptr` 42 // must point to a valid `HrTimer` instance. 43 unsafe { HrTimer::<T>::raw_cancel(timer_ptr) } 44 } 45 } 46 47 impl<T, A> Drop for BoxHrTimerHandle<T, A> 48 where 49 T: HasHrTimer<T>, 50 A: crate::alloc::Allocator, 51 { 52 fn drop(&mut self) { 53 self.cancel(); 54 // SAFETY: By type invariant, `self.inner` came from a `Box::into_raw` 55 // call. 56 drop(unsafe { Box::<T, A>::from_raw(self.inner.as_ptr()) }) 57 } 58 } 59 60 impl<T, A> HrTimerPointer for Pin<Box<T, A>> 61 where 62 T: 'static, 63 T: Send + Sync, 64 T: HasHrTimer<T>, 65 T: for<'a> HrTimerCallback<Pointer<'a> = Pin<Box<T, A>>>, 66 A: crate::alloc::Allocator, 67 { 68 type TimerMode = <T as HasHrTimer<T>>::TimerMode; 69 type TimerHandle = BoxHrTimerHandle<T, A>; 70 71 fn start( 72 self, 73 expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires, 74 ) -> Self::TimerHandle { 75 // SAFETY: 76 // - We will not move out of this box during timer callback (we pass an 77 // immutable reference to the callback). 78 // - `Box::into_raw` is guaranteed to return a valid pointer. 79 let inner = 80 unsafe { NonNull::new_unchecked(Box::into_raw(Pin::into_inner_unchecked(self))) }; 81 82 // SAFETY: 83 // - We keep `self` alive by wrapping it in a handle below. 84 // - Since we generate the pointer passed to `start` from a valid 85 // reference, it is a valid pointer. 86 unsafe { T::start(inner.as_ptr(), expires) }; 87 88 // INVARIANT: `inner` came from `Box::into_raw` above. 89 BoxHrTimerHandle { 90 inner, 91 _p: core::marker::PhantomData, 92 } 93 } 94 } 95 96 impl<T, A> RawHrTimerCallback for Pin<Box<T, A>> 97 where 98 T: 'static, 99 T: HasHrTimer<T>, 100 T: for<'a> HrTimerCallback<Pointer<'a> = Pin<Box<T, A>>>, 101 A: crate::alloc::Allocator, 102 { 103 type CallbackTarget<'a> = Pin<&'a mut T>; 104 105 unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart { 106 // `HrTimer` is `repr(C)` 107 let timer_ptr = ptr.cast::<super::HrTimer<T>>(); 108 109 // SAFETY: By C API contract `ptr` is the pointer we passed when 110 // queuing the timer, so it is a `HrTimer<T>` embedded in a `T`. 111 let data_ptr = unsafe { T::timer_container_of(timer_ptr) }; 112 113 // SAFETY: 114 // - As per the safety requirements of the trait `HrTimerHandle`, the 115 // `BoxHrTimerHandle` associated with this timer is guaranteed to 116 // be alive until this method returns. That handle owns the `T` 117 // behind `data_ptr` thus guaranteeing the validity of 118 // the reference created below. 119 // - As `data_ptr` comes from a `Pin<Box<T>>`, only pinned references to 120 // `data_ptr` exist. 121 let data_mut_ref = unsafe { Pin::new_unchecked(&mut *data_ptr) }; 122 123 // SAFETY: 124 // - By C API contract `timer_ptr` is the pointer that we passed when queuing the timer, so 125 // it is a valid pointer to a `HrTimer<T>` embedded in a `T`. 126 // - We are within `RawHrTimerCallback::run` 127 let context = unsafe { HrTimerCallbackContext::from_raw(timer_ptr) }; 128 129 T::run(data_mut_ref, context).into_c() 130 } 131 } 132